During the use and transportation of shells, there is a great risk that these will be exposed to shell splinters or fire from small-bore ammunition which can result in the shells detonating. In order to avoid or minimize the risk of the active part in a shell detonating, low-sensitive explosives are currently used, called insensitive munitions, abbreviation IM. A disadvantage of these explosives is that they have a much greater coefficient of thermal expansion than other materials normally comprised in an active part, such as aluminium, copper and iron in the liner or penetrating body and aluminium in the casing. As a shell is designed to be able to be used within a temperature range of more than 100° C., it is thus a question of large differences in the thermal expansion of the materials of which it is made. With temperature differences of the size stated, gaps can easily arise between the active part's liner and its explosive charge and between the active part's casing and its explosive charge due to differences in the coefficients of thermal expansion. These gaps eliminate or interfere with the hollow charge effect of the active part and risk setting off an unintentional detonation of the explosive charge.
The problem with differential thermal expansion is previously known in connection with ammunition, see for example GB 2 198 817. This document states that the explosive charge normally has a very much higher thermal expansion than the casing and liner. According to the application, the introduction is proposed of a specially-shaped sprung washer which is in contact with the liner of the explosive charge and engages in the casing of the charge.
When an explosive charge contained in the casing of an active part is subjected to a high temperature, there is also a great risk that the explosive charge will detonate. In order to eliminate this risk, the explosive charge should be able to be released from the interior of the active part.